Antisera prepared against electrophoretically homogeneous glyceraldehyde-3-phosphate dehydrogenases from Streptococcus faecalis, Pediococcus cerevisiae and Lactobacillus acidophilus are being used to verify the phylogenetic map of lactic acid bacteria and related organisms constructed from a previous study of the enzyme fructose diphosphate aldolase. Studies with the latter two antisera have been instrumental in relating the genus Leuconostoc to this large group of bacteria as well as ordering heterofermentative species of lactobacilli not included in earlier surveys. Work has been expanded to include a group of hitherto underscribed enzymes responsible for pentitol dissimilation. Certain strains of streptobacteria are capable of growing at the expense of ribitol, xylitol, D-arabitol or L-arabitol by inducing specific transport systems and dehydrogenases that convert pentitol to keto-pentose-5-phosphate. The intermediate product then enters a central metabolic pathway and is converted to acidic end products. BIBLIOGRAPHIC REFERENCES: London, J.: The ecology and taxonomic status of the lactobacilli. In Starr, M.P. (Ed.): Annual Reviews of Microbiology. Ann. Rev. Microbiol. 30: 279-301, 1976. London, J. and Chace, N.M.: A new pathway for the metabolism of pentitols. Proc. Natl. Acad. Sci. 1977, in press.